1. Technical Field
The present invention relates to a light emitting device, more particularly to a light emitting diode package manufactured by putting thermoplastic polymer into a previously produced mold and by using a compression molding method or an injection molding method, and a manufacturing method thereof.
2. Description of the Related Art
With a light emitting diode (LED), wide markets related to a signboard, a display, an automobile, a signal light, a backlight and general illumination are now being formed. The LED market is steadily growing in each of the application fields. Particularly, various small-sized display devices having a low energy consumption rate are recently developed and a liquid Crystal Display (LCD) is popular with display devices, for example, a monitor, a laptop computer and a mobile communication terminal and the like. However, since the LCD cannot voluntarily generate a light beam, it is common to include a backlight used as a light source generating a light beam on the rear surface or the side surface of the LCD panel. A cold cathod fluorescent lamp (CCFL) and the LED are mainly used as such a backlight light source.
But, since the CCFL uses mercury vapor, the CCFL has disadvantages in that it may cause environmental pollution, has a slow response speed and poor color reproductivity and is not suitable for causing the backlight light source to be light, thin, short and small due to the big size thereof.
In comparison with this, the LED has advantages in that it is environmentally friendly and has a high response speed of several nanoseconds, a long life and high crashworthiness. The LED can freely change luminance and color temperature, etc. by adjusting the light amount of red, green and blue LEDs so that it has superb color reproductivity and is more suitable for causing the backlight light source to be light, thin, short and small. Accordingly, a side light emitting type LED package adopting the LED is mainly used as a backlight light source used in small-sized devices such as a mobile phone, a car navigation system and a PMP and so on.
Such an LED package for the backlight light source should include design flexibility capable of increasing the angle of orientation for maximizing the efficiency of an LED chip, and should be able to mount a large number of the LEDs in order to acquire the certain brightness. As electronic communication devices and display devices are smaller and thinner, the LED package is required to be thinner and lighter and the material cost and process cost is also required to be reduced.
FIG. 1 illustrates a side view of the structure of an LED package adopting a lead frame structure according to the related art.
Referring to FIG. 1, an LED package adopting the lead frame structure according to the related art is manufactured by mounting the LED chip 40 on the upper surface of a lead frame 20, and then performing wire bonding 50 and injecting molding resin 60 into the inside of injection molded products 10 and 30 surrounding the lead frame 20. However, in the LED package adopting the lead frame as illustrated in FIG. 1, there are problems in that it is difficult to cause the LED package to be light and thin due to the weight of the lead frame, and total material cost rises because of the high price of own lead frame. Also, there is a problem in that there is a limit in increasing the angle of orientation (light-emitting angle) of the LED package owing to the significant restriction for chip design, which is caused by an arrangement of the lead frame.
In order to solve such problems, an LED package using low temperature co-fired ceramic (LTCC) is provided in substitution for the lead frame structure mentioned above. FIG. 2 illustrates a side view of the structure of an LED package using low temperature co-fired ceramic (LTCC) according to the related art.
Referring to FIG. 2, the LED package using LTCC includes a lower ceramic sheet 11, electrode 21, an upper ceramic sheet 31, a reflector 32, an LED chip 41, a wire-bonding, 51 and molding resin 61. However, even though such an LED package using LTCC can be replaced with the conventional lead frame structure in that cavity process can be applied to the LED package using LTCC by punching, and the LED package can be made by the lamination process of numerous ceramic sheets, there are still the following problems.
First, since the LED package using LTCC makes use of a ceramic substrate, the material cost thereof is high. It is difficult to mount numbers of LED chips on one substrate because the larger the size of the substrate is, the higher the possibility of occurrence of crack is. In addition, since the ceramic substrate has a different coefficient of thermal expansion from that of the molding resin, errors such as separation of the wire bonding may occur.
Additionally, since the LED package using LTCC adopts the existing ceramic substrate process as it stands when manufacturing the package, the LED package manufacturing process is complicated. This can be easily cleared through a flowchart of an LED package manufacturing method using LTCC illustrated in FIG. 3.
In step of S10 in FIG. 3, an upper ceramic sheet 31 having a through portion at the central part thereof is manufactured with the ceramic sheet 31A previously prepared through the cutting process by means of a punching process or a laser drill. In step of S20 in FIG. 3, the electrode 21 is formed on the lower ceramic sheet 11.
In step S30 of FIG. 3, the upper ceramic sheet 31 is laminated on the upper side of the lower ceramic sheet 11 having the electrode 21. A space for mounting the LED chip 41 in the future, that is, a cavity is formed on the upper surface of the lower ceramic sheet 11 through such a lamination process. In step of S40 in FIG. 3, the lower ceramic sheet 11 and the upper ceramic sheet 31 are fired.
In step of S50 in FIG. 3, the reflectors 32 are formed on the side walls of the upper ceramic sheet 31. In step of S60 in FIG. 3, the LED chip 41 is mounted in the cavity formed on the upper surface of the lower ceramic sheet 11, and the wire bonding 51 is performed so that the LED chip 41 is electrically connected to the electrode 21. In step of S70 in FIG. 3, the cavity formed on the upper surface of the lower ceramic sheet 11 is filled with molding resin 61 so that the LED chip 41 and the wire bonding 51 are fixed and sealed.
As described above, in the case of the LED package manufacturing method using LTCC, it can be seen that many procedures, that is, the punching/cutting process, the lamination process and the firing process, should be applied in the order specified so as to form the cavity, i.e., a space for mounting the LED chip 41. Also, in the cavity manufactured by the punching/cutting process and the lamination process, the boundary surface thereof always forms a right angle so that it is hard to obtain the wide angle of orientation (light-emitting angle) in the LED package.